You got that out of the document presumably, and that is really just being used for my personal organization, meaning it probably won't make any sense (so just ignore it). As long as you build only inside the box, it should be clear that you start from the checkpoint pointing inward and end at the one pointing outward. How you connect them is up to you.
Yes, however, you do need to start and end on the upper levels of the CPs.
Cxom says:
As to Marius, yes, my issue was that only one can be placed. If you could maybe set it up well and show/send it to me I'll consider it, but I'm nevertheless tentative given the aforementioned restriction.
And as to mgafmuat, that idea, although doable, quite negates the idea of "flow" or continuity in a track. When you're going to be racing for a few hours on a track, you do not want to suddenly encounter a forced respawn. I am additionally not keen on having to use MT for any sort of wayfinding in the track; it should be natural and intuitive.